Plutonium fallout reconstructed from an Antarctic Plateau snowpack using inductively coupled plasma sector field mass spectrometry

Abstract

Anthropogenic plutonium (Pu) in the environment is a result of atmospheric nuclear testing during the second half of the 20th century. In this work, we analyzed a 4-meter deep Antarctic Plateau snowpack characterized by a lowsnowaccumulation rate and negligible snowimpurities. These sample conditions enabled us to measure the snowpack Pu fallout by applying inductively coupled plasma sector field mass spectrometry to a few mL of snow melt without purification or preconcentration. Pu concentrations in the reconstructed Pu fallout record for the period after 1956 CE increased and decreased in agreement with past atmospheric nuclear testing. Two peaks and two dips associable with historical events were observed, and the highest peak in 1964(±1) CE approximately coincided with the maximum concentration of non-sea-salt sulfate caused by the Mt. Agung eruption in 1963 CE. Enhanced Pu fallout in the 1970s was attributed the geographical proximity of the Southern Hemispheric nuclear test sites. Our results suggest that by improving the instrumental sensitivity and precision, the potential of the Antarctic ice sheet as an archive of Pu fallout can be further explored and utilized for understanding atmospheric dispersion and for dating ice cores.